Clarification of blood serum and plasma using a block copolymer of ethylene oxide and polyoxypropylene

ABSTRACT

A method of clarifying blood serum and plasma to remove undesired proteinaceous and lipid particulate matter which comprises admixing the serum or plasma with from greater than about 20 to about 30% of block copolymers of ethylene oxide and polyoxypropylene polymer.

United States Patent Fekete et al. July 8, 1975 [54] CLARIFICATION OF BLOOD SERUM AND 2,533,004 12/1950 Ferry et a1. 424/101 PLASMA USING A BLOCK COPOLYMER fifl ii 31 1354 0 we e a 0F ETHYLENE OXIDE AND 3,395,210 7/1968 Lenahan et a1. 424/11 POLYOXYPROPYLENE 3,450,502 6/1969 Hymes 424/101 [75] Inventors: Lajos F. Fekete, Costa Mesa; Frank Q F yme gj g Laghna Beach both 3,839,314 10 1974 Fekete et a1. 260/112 B [73] Assignee: Baxter Laboratories, Inc., Morton Grove Ill Przmary Exammer1-loward E. Scham Attorney, Agent, or Firm-Scott J. Meyer; Louis [22] Filed: Apr. 1, 1974 Al [21] Appl. No.: 456,698

Related U.S. Application Data ABSTRACT [60] Continuation of Ser, No. 348,463, April 5, 1973,

abandoned, which is a division of Ser. No. 158,111, A method f Clarifying blood serum and plasma to June 1971 move undesired proteinaceous and lipid particulate matter which comprises admixing the serum or plasma [52] U.S. Cl. 260/112-B; 424/177 with from greater than about 20 to about 30% of Cl- 1 block copolymers of ethylene Oxide and p yo ypro [58] Field of Search 260/1 12 B pylene p01ymer [56] References Cited 2 Uaim's, N0 Drawings CLARTFICATEION OF BLOOD SERUM AND PLASMA USING A BLQCK COPCLYMER OF ETHYlLlENE OXIDE AND PULYQXYPROPYLIENE This is a continuation, of application Ser. No. 348,463, filed Apr. 5, 1973 now abandoned, said 348,463 being a Division of Ser. No. 158,111 filed June 29, 1971 now US. Pat. No. 3,770,631.

This invention relates to a method of separating proteinaccous and lipid materials from blood serum and plasma.

Blood comprises a fluid containing the red and the white blood cells and the blood platelets. The plasma, or fluid part of blood, contains about 90% water and 10% solids. These solids consist essentially of about 7-9% proteins, 1% salts, and the remainder lipids and other substances. Freshly drawn blood clots within a few minutes. Formation ofthe clot is a complex process in which the protein, fibrinogen, is converted into insoluble fibrin. Blood serum is plasma from which this fibrin has been removed.

Fractionation of blood plasma and serum and the laboratory and clinical use of the separated blood components is common practice today. Among the various components separated from blood are albumin, globulins, a- -globulins, B-globulins, 67 =globulins, fibrinogen, prothrombin, antihemophilic globulin, lipoproteins, thromoboplastic, complement components, isoagglutinins, cholesterol, phosphatides, and numerous enzymes, e.g., amylase, fibrinolysin, esterase, and phosphatase. Various methods have been developed heretofore for separating and purifying the foregoing and other blood components. These methods generally comprise one or more of the following procedures:

a. fractional precipitation with ammonium sulfate and similar salts;

b. organic solvent precipitation with cold ethanol or acetone and other such alcohols and ketones;

c. selective absorption on calcium phosphate gels or with barium sulfate;

d. isoelectric precipitation by pH adjustment to the point at which there is no net charge on a given protein; and

e. chromatography by use of absorbents such as CM- or DEAE-cellulose or by Sephadex gel filtration.

Other more recently developed procedures for selectively fractionating and purifying blood proteins involve the use of amino acids such as glycine and beta alanine, water-soluble organic polymers such as polyethylene glycol and polypropylene glycol, and waterinsoluble polyelectrolyte polymers containing basic amino groups such as the dimethylaminopropylimide group.

In accordance with the present invention, a new and improved method is provided for separating proteinaceous and lipid materials from blood serum and plasma. The method comprises selective precipitation with certain block copolymers which are ethylene oxide-propylene glycol condensation products. Separation of the blood components with these block copolymers has been found to be substantially and significantly better than with the polymeric polyethylene glycol. These improvements consist of increased yield and The ethylene oxide-propylene glycol condensation products employed in this invention can be prepared by condensing ethylene oxide with polyoxypropylene polymer. A further description of the preparation of these block copolymers if found in US. Pat. No. 2,674,619. These block copolymers can be represented by the following structural formula:

HO(CH Cl-l O),, (CHCH O),, (cam-1 o H For purposes of this invention, these block copolymers desirably contain at least 50% ethylene oxide in the molecule and a polyoxypropylene hydrophobic base molecular weight of at least 950. Materials containing less than 50% ethylene oxide are not sufficiently nontoxic and products having a hydrophobic base molecular weight less than 950 do not have the desired solubility. in this respect, the block copolymers employed in this invention are related to and include materials used as blood plasma substitutes and for priming heart-lung apparatus as described in Belgian Pat. No. 721,138 and US. Pat. Nos. 3,450,502 and 3,577,522.

lllustrative examples of suitable block copolymers are the F-38 and 1 -68 PLURONIC polyols sold by Wyandotte Chemicals Corp. F-38 contains of polyoxyethylene hydrophilic units in the molecule and the polyoxypropylene hydrophobic base has a molecular weight of 950. lF-68 also contains 80% of polyoxyethylene hydrophilic units in the molecule but the hydrophobic base has a molecular weight of 1750. The total molecular weight of these two PLURONlC polyois is 4750 and 8750, respectively. A further description of these polyols is found in the bulletin of Wyandotte Chemicals Corp. The Pluronic Grid, Sixth Edition.

The amount of block copolymer employed in the separation process of this invention can vary, depending in part on the particular proteinaceous or lipid fraction to be precipitated from the blood plasma or serum. In general, from about 1 to about 30% of the copolymer on a basis of weight per volume of the plasma or serum is employed. Relatively low levels of the block copolymer, for example, from about 1 to about 20% are generally employed for fractionating specific protein materials which are desired to be retained for laboratory and clinical use. Higher levels of the block copolymer, for example, from greater than about 20 to about 30%, are preferred for removing substantially all undesired proteinaceous and lipid particulate matter from the blood plasma or serum. This is achieved by precipitating a product at this concentration of copolymer which can be separated from said particulate matter, which is soluble and remains in the supernatant. The precipitate can then be redissolved to form a crystal clear serum.

The precipitation can be conducted at ordinary room temperature (about 25C) but colder temperatures are generally preferred since proteinaceous materials are known to be subject to heat denaturation and optimum potency is retained in the proteinaceous material by maintaining cold temperatures of from about 4C to about 25C.

In some instances it is useful to employ the block copolymer agents in combination with certain other substances which are essentially precipitation or absorption agents In particular, glycine, tricalcium phosphate and diatomaceous earth are frequently advantageously employed in conjunction with the blockcopolymers. The step in the separation process at which these other agents are employed and the amounts used will vary, depending in part on the particular proteinaceous or lipid material desired to be precipitated. Generally from about 0.5 to 2% of the tricalcium phosphate, about 0.1 to 0.5% of the diatomaceous earth, and about 2 to 3 molar glycine are suitable in these instances.

The following specific examples will illustrate the invention as it applies to particular to the preparation of antihemophilic globulin and prothrombin coagulation factors, to thromboplastin controls, and to the preparation of clarified serums for organ perfusates and for use as blood grouping and typing serums. It will be appreci- EXAMPLE 1 The preparation of plasma for use as an organ perfusion fluid. Plasma that has been collected in anticoagulant is first treated by admixing with glycine to a molarity of 2 to 3 respective of glycine at pH 6.88 in the cold (8C) for 30 to 45 minutes. The precipitate that forms is discarded and the remaining supernatant fluid is diluted 1:1 with normal saline (0.85% NaCl solution). From above 20 to about 30% (wt/vol.) of PLU- RONIC F38 is then added at pH 6.5 to 7.0 and the mixture stirred for 30 minutes at room temperature. The supernatant fluid is discarded and the remaining precipitate dissolved in normal saline solution to a level of approximately the original plasma volume. To this solution is added 0.5% (wt./vol.) of tricalcium phosphate at pH 7.2. The suspension is mixed for 15-60 minutes at room temperature (25C). The precipitate that is formed is discarded and the supernatant fluid is retained. To the supernatant fluid is added sodium citrate to a concentration of 0.02 M. The pH is adjusted to 7.5 and the fluid is then heat treated at 37C for 24 to 120 hours until the level of coagulation Factor V (proaccelerin) is decreased to approximately zero percent. Then 0..l% (wt./vol.) CELITE diatomaceous earth filter aid is added and the fluid mixed for minutes at room temperature. The resulting precipitate is discarded and the remaining supernatantfluid is sterile filtered through a MILLIPORE filter'(0.3 microns). The retained fluid is stable in storage and is crystal clear in appearance. It is eminently suitable for use as an organ perfusion fluid, for example, a kidney, heart or lung perfusion fluid.

In the above Example, the glycine precipitation step removes essentially all the Factor VIII and fibrinogen, the PLURONIC F-38 precipitation step removes essentially all the lipoprotein and residual fibrinogen, the tricalcium phosphate absorption step removes Factors II, VII, IX and X, the heating at 37C inactivates Factor V and the CELITE absorption step removes Factors XI and XII.

EXAMPLE 2 The preparation of serum for use as blood grouping and typing serums. The serum to be clarified is first diluted with normal saline (0.85% NaCl solution) so that the protein concentration is between about 2.5 and 3.0 grams/100 ml. The pH is adjusted to 6.5-7.0 and then from above to about 30% of PLURONIC F-38 (preferably about 24 grams/8O ml.) is added at room temperature and mixed for 30 to 60 minutes. The supernatant', which contains lipoprotein and fibrous materials,'is discarded-and to the remaining precipitate is added sufficient normal saline to adjust the volume to a level of about the original serum volume. The pH is adjusted to 7.2 and then 0.5%.,(wt./vol.) of tricalcium phosphate is added to thedissolved precipitate. The suspension is mixed'for-30 minutes at room temperature. The mixture is then centrifuged to clarify the serum and the resulting supernatant serum is carefully decanted from the tricalcium phosphate and activated clotting factors complex and retained for blood banking use. This procedure is suitable, for example, for the clarification of (a) Anti-A and Anti-B blood grouping serums, and (b) Anti-c and Anti-e typing serums for the saline tube test.

EXAMPLE 3 The preparation of an AHF concentrate for clinical use. To prepare a potent antihemophilic factor (AHF Factor VIII) concentrate by fractionation with PLU- RONIC F-38, the following procedure is followed:

Whole blood is collected in 4% citrate anticoagulant solution (1 part of 4% citrate anticoagulant solution plus 9 parts of whole blood); the cells are separated from the plasma by centrifugation; the retained plasma is frozen at 25C and then thawed at 45C; and the resulting cryoprecipitate is collected by centrifugation.

The cryoprecipitate is dissolved in 0.1 molar glycinecitrated saline (one part 0.1M sodium citrate in four parts by weight 0.9% saline made 0.1M respective of glycine) at 2225C (room temperature) and the pH is adjusted to 6.5 with 1 normal acetic acid. Solid PLURONIC F-38, 3.5% (wt./vol.), is added and the suspension mixed for 15 minutes at 22-25C. The mixture is centrifuged for 30 minutes at 5000 RPM and the resulting precipitate (fibrinogen) is discarded.

The AHF-rich supernatant is collected and the pH is adjusted to 6.88 with 1N NaOH. Solid PLURONIC F-38 is then added to a final concentration of 10% (wt./vol.) and the suspension is mixed for 15 minutes at 2225C. The mixture is centrifuged for 30 minutes at 5000 RPM and the supernatant is discarded.

The remaining AHF precipitate obtained by the second centrifugation is dissolved in citrated saline (one part of 0.1M sodium citrate in four parts by weight 0.9% saline) to a final potency of 20 to 30 AHF units per ml. As used herein, an AHF unit is equivalent to the AHF activity in one ml. of pooled normal whole plasma. The dissolved product is sterile filtered with a MILLIPORE membrane filter using pore sizes of 0.3g, 0.45p., and 0.2p.. The filtered solution is then filled under asceptic conditions in 10 ml. to 30 ml. capacity vials, rapidly frozen and lyophilized. Upon reconstitution with sterile water, the final product is suitable for administration to hemophiliac patients suffering bleeding episodes.

EXAMPLE 4 The preparation of a prothrombin complex for clinical use. To prepare a potent prothrombin complex (Factor II plus other clotting factors) by fractionation with PLURONIC F-38, the, followingprocedure is followed:

Cohn plasma fraction lV-l is suspended in normal saline (0.9 NaCl solution) to a concentration of 10% (wt/vol.) and the pH is adjusted'to-7.2. Triabasic calcium phosphate (500 grams) is then added to 50 liters of the fraction lV-l suspension and the mixture is stirred for about 30 minutes. The suspension is then centrifuged and the supernatant is discarded. The re tained precipitate is suspended in 0.1M trisodium citrate to a final volume of liters. The suspension is centrifuged and the precipitate is discarded. The pH of the retained supernatant is adjusted to 7.2, PLURONIC" F-38 is added to a final concentration of 5%, and the suspension stirred for about minutes. Thesuspension is clarified by centrifugation, with retention of the supernatant and discarding of the precipitate. The pH of the retained supernatant is then adjusted to 5.2, and PLURONTC R38 is added to a final concentration of The suspension is centrifuged and the precipitate that is recovered is dissolved in citrated saline to a volume of 5 liters. Heparin is added in an amount of one unit per rnl., and the dissolved product is sterile filtered with a MlLLllPURlE membrane filter using pore sizes of 0.3a, 0.45 and 0.2;.t. The filtered solution is then filled under aseptic conditions in 10 ml. to 30 ml. capacity vials, rapidly frozen and lyophilized. Upon reconstitution with sterile water, the final product is suitable for administration to patients deficient in lFactor ii.

In Examples 3 and 4, above, it is found that the separation of the respective desired protein precipitate is achieved more rapidly than is the case when polyethylene glycol 4000 is used in place of the PLUIRONIC lF-38 and the yield of the final product is substantially increased.

EXAMPLE 5 The preparation of a thromboplastin control from plasma. Fresh human blood is collected in 4% sodium citrate anticoagulant solution (1 part of anticoagulant and 9 parts of whole blood). The resulting mixture is centrifuged at 3000 X0 at 5C. The resulting supernatant plasma is centrifuged again in the same manner as before and then frozen at 20C. The plasma is thawed at room temperature (ca. C) and diluted with 0.9% physiologically normal saline solution (1 part of plasma and 1 part of normal saline solution). The pH of the resulting solution is adjusted to 6.0-7.0 with 1N l-lCl. PLURONTC P38 is then added to the solution to a final concentration of to form a precipitate. After centrifugation, excess citrate and trace amounts of thromboplastic active material are removed in the supernatant, which is discarded.

The above-prepared plasma is then used to prepare several thromboplastin controls for use in making prothrombin time determinations such as by the Quick one-stage prothrombin time test or the modified Owren prothrombin test as described in the Hyland Reference Manual of Coagulation Procedures, published by Hyland Laboratories, Los Angeles, Calif, pp. l0-l4 (2d. ed. 1964). These controls are made to resemble physiological plasma by employing as the sole buffering agent for the plasma l) citrate-imidazolenormal saline buffer, or (2) oxalate-imidazole-normal saline buffer, consisting of the following components:

1. -Citrate-imidazole-normal saline buffer 0.9% NaQl solution 0.0135 molari0.005 tri-sodium citrate 0.025 to 0.035% imidazole 2. Oxalate-imidazole-normal saline buffer 0.9% NaCl solution 0.0135 molari0.005 sodium oxalate 0.025 to 0.035% imidazole By using the foregoing amounts of the citrate or oxalate anticoagulants in said buffer, undesirable activation of the clotting factors and thromboplastin generation are effectively prevented. Excess citrate and traces of thromboplastic active material are removed, as hereinbefore provided, by the initial employment of the PLURQNIIC F38 treatment on the plasma. With these combined steps, maximum stabilization of the thromboplastin controls is achieved.

The citrate controls (100% and 20% controls) are prepared as follows:

For the 100% control, the precipitant paste from the PLURONTC lF-38 treatment is dissolved in the citrate-imidazole-normal saline buffer to 50% to of the original volume of the plasma.

For the 20% control, the precipitant paste from the PLURONTC lF-38 treatment is dissolved in normal saline to to 120% of the original volume of the plasma. lProthrombin-free human plasma is then prepared from the redissolved precipitant paste by adsorbing out the prothrombin complex (lFactors ll, Vll, TX and X). This adsorption is achieved by adding tricalcium phosphate to a final concentration of 1% by weight, adjusting the pH to 7.2' "0.2 with 1 normal HC], and mixing for about 30 to 45 minutes. The suspension is then centrifuged. The supernatant is buffered with 0.0135Mi0005 trisodium citrate and 0.025 to 0.035% imidazole, and the pT-l adjusted to 7.8:02 with 1 normal NaOlHl. This solution is then mixed with the appropriate volume of the above-prepared citrate control to provide the desired clotting times for the 20% control.

The 100% and 20% oxalate controls are prepared in the same manner as the above-prepared citrate controls except that 0.0135M sodium oxalate is used in place of 0.0135lVl trisodium citrate.

Various other examples and modifications of the foregoing examples will be apparent to those skilled in the art. For example, albumin, fi-globulins, fibrinogen and other blood fractions can also be obtained by employing the separation procedure of this invention. All such further examples and modifications as come within the spirit and scope of the invention are included herein.

What is claimed is:

l. The process in which a clarified plasma for use as a thromboplastin control is obtained from blood plasma by admixing said blood plasma with a compound of the formula irorci-ncn or, icncmo cri cri oxu wherein a and c are integers such that the hydrophile portion represented by (CT-l CH 0) constitutes at least about 50% of the molecule and b is an integer such that the hydrophobic portion represented by has a molecular weight of at least about 950 to a con centration of from greater than about to about 30% on a weight per volume basis of said compound and at a pH of 6 to 7, admixing the resulting precipitate in normal physiological saline to 80 to 120% of the original volume of said blood plasma, admixing the resulting mixture with from about 0.5 to about 2% tribasic calcium phosphate at a pH of 7 to 7.4, removing the resulting precipitate andadmixing the supernatant with aqueous buffer selected from the group consisting of (a) citrate-imidazole buffer comprising from about 0.0130 molar to 0.0140 molar trisodium citrate and about 0.025 to 0.035% imidazole and (b) oxalateimidazole buffer comprising from about 0.0130 molar to 0.0140 molar sodium oxalate and about 0.025 to 0.035%v imidazole, said buffers adjusted to pH 7.6 to 8.0.

' 2. The process of claim 1 in which said compound contains about of polyoxyethylene hydrophilic units in the molecule and the polyoxypropylene hydro- ;phogic base has a molecular weight of 950. 

1. THE PROCESS IN WHICH A CLARIFIED PLASMA FOR USE AS A THROMBOPLASTIN CONTROL IS OBTAINED FROM BLOOD PLASMA BY ADMIXING SAID BLOOD PLASMA WITH A COMPOUND OF THE FORMULA
 2. The process of claim 1 in which said compound contains about 80% of polyoxyethylene hydrophilic units in the molecule and the polyoxypropylene hydrophogic base has a molecular weight of
 950. 